DE19943034A1 - Powder coating crosslinkers with high functionality and containing uretdione groups and free isocyanate groups - Google Patents

Abstract

The invention relates to new, highly functional polyaddition compounds containing uretdione groups, a process for their production and their use as starting components in the production of polyurethane plastics, in particular as crosslinkers for heat-crosslinkable powder coatings.

Description

The invention relates to new, highly functional poly containing uretdione groups addition compounds, a process for their preparation and their use as Starting component in the production of polyurethane plastics, esp especially as a crosslinker for heat-crosslinkable powder coatings.

As a blocking agent-free crosslinker for highly weather-resistant polyurethane (PUR) - Today, powder coatings are increasingly finding uretdione groups Polyaddition compounds use. As a networking principle, these Compounds the thermal cleavage of the uretdione structures into free iso cyanate groups and their subsequent reaction with a hydroxy-functional Used binders.

Although uretdione powder crosslinkers have been known for a long time, they could have not yet made a decisive contribution to the market. The reason for this is inter alia. to the a comparatively low isocyanate content of the currently commercially ver addable products, on the other hand in their low average functionality, the is often even less than 2.0. With regard to sufficient networking dense, in paints and coatings synonymous with good resistance properties, but are precisely crosslinking components with a high NCO content and the highest possible functionality of at least 2.0 is desirable.

EP-A 45 994 describes reaction products of a linear, difunctional one IPDI uretdione and insufficient amounts of simple, optionally ether oxygen containing diols as blocking agent-free powder coating crosslinkers. This polyaddi tion products containing up to 8% by weight of unblocked free isocyanate at the end may have groups, although they are characterized by high total isocyanate contents (Sum of free and internally blocked uretdione groups Isocyanate groups) and a functionality of 2.0, their production, in particular on a technical scale, however, is difficult.

Since the cleavage of the thermolabile uretdione structures in the presence of hy Droxy-functional reaction partners starts noticeably at 110 ° C this temperature in the synthesis of polyaddition compounds containing uretdione groups should not be exceeded if possible. Show in this temperature range however, the products described in EP-A 45 994 have such high melt viscosities would do that their producibility in the melt due to the inadequate Stirability on an industrial scale reaches its limits. Large-scale can be such uretdione crosslinkers only ge in solvents which are inert towards isocyanates solves produce. Then, in an additional process step, the Auxiliary solvents are separated. A solvent described in EP-A 669 354 Tel-free manufacturing process for such polyaddition compounds in which the starting materials in special reaction screws or extruders under the action of high shear Forces can be implemented with each other, however, is very expensive in terms of equipment and expensive.

The main disadvantage of the polyadducts described in EP-A 45 994 is but in the relatively high content of unblocked free isocyanate groups, which already during powder coating production, usually by melt extrusion at approx. 100 ° C, react with the hydroxy-functional binder. Such pre-networked Powder coatings show such an unfavorable rheological behavior during the stoving process, that they lead to coatings with only moderate optical properties, in particular a completely inadequate course, harden.

The problem of undesired pre-crosslinking exists in principle for all of them PUR powder coating hardeners that have a high content of free isocyanate groups. For example in the case of the blockies described in EP-A 45 996 and EP-A 45 998 Medium-free powder coating crosslinkers made from linear IPDI uretdione and simple Diols are therefore at least partially with the terminal free isocyanate groups Monoamines or monoalcohols implemented. In this way the disturbing Pre-reaction in the extruder can be prevented, the chain termination with a monofunk functional compound, however, significantly reduces the total isocyanate content, at the same time, the mean functionality drops to values below 2.0. Furthermore also point the products of these two publications in the field of re cleavage temperature of uretdione groups so high melt viscosities that they safe and reproducible only in solution or according to the complex process of EP-A 669 354 can be produced.

The production of uretdione powder lacquer crosslinkers using ester chain extenders containing groups or carbonate groups is the subject matter of EP-A 639 598. The products obtainable by this process already have Temperatures only slightly above their melting point, so low melt viscosities would result in solvent-free production in simple stirring equipment for the first time becomes possible. The uretdione crosslinkers described in EP-A 720 994 are also included which dimer diols are used for chain extension, have a solution medium-free production of sufficiently low melt viscosities. Because of the relative high molecular weight of the chain extenders used, the Pro products of both publications, however, compared to those of EP-A 45 996 again decreased total isocyanate levels.

According to the teaching of EP-A 669 353, solvent-free implementation linear IPDI dimers with molar excess amounts of diols and / or Polyester diols in special intensive kneaders containing uretdione groups, terminal Polyurethanes containing hydroxyl groups and an average functionality of 2.0 produce. The use of at least trifunctional polyols and / or ver allows branched polyester polyols, as in EP-A 825 214 or EP-A 780 417 shown even the production of OH-terminated uretdione crosslinkers with Functionalities between 2 and 3 or ≧ 3. The advantage of high functionality is opposed to these polyaddition compounds, however, as a disadvantage that the hydroxyl groups present in the crosslinker molecule under stoving conditions also react with urethanization and so for the crosslinking of the bandage Significantly reduce by means of the available, internally blocked NCO content.

From EP-A 760 380 are uretdione powder lacquer crosslinkers with high latent NCO Contained on the basis of HDI dimers which may contain isocyanurate groups known. As on page 5, lines 28 to 30 and page 7, lines 7 to 9 of this publication However, products with an excessively high isocyanurate content or Degree of branching to coatings with poor optical and also mecha niche properties. In the production of polyurethane hardeners according to EP-A 760 380 are therefore branched starting polyisocyanates containing isocyanurate groups generally through the use of monofunctional structural components largely "linearized".

Polyaddition products containing uretdione and isocyanurate groups from one IPDI dimerisate, diols and / or di prepared by trialkylphosphine catalysis secondary diamines as chain extenders and optionally monoalcohols or Monoamines are the subject of EP-A 790 266. These products can be used at high Functionality also relatively high proportions of free isocyanate groups and thus have a high total isocyanate content, their production succeeds due to of the highly branched starting polyisocyanate, however, exclusively in orga niche solution.

So far, no uretdione powder lacquer crosslinkers are known, all of which Requirements in practice are sufficient and in particular high total levels of iso have cyanate groups with the highest possible crosslinking functionality and the same are readily accessible in a simple process.

The object of the present invention was therefore to provide PU containing uretdione groups To provide powder coating crosslinkers that do not follow the above-mentioned have parts of the prior art.

This task could be accomplished with the provision of the below described in more detail Polyaddition compounds according to the invention or the process for their Her position to be solved. The invention described in more detail below Polyaddition compounds are based on the surprising observation that by reacting branched ones containing uretdione and isocyanurate groups Polyisocyanate mixtures with insufficient molar amounts of ester and / or carbo Polyols containing natgruppen in a solvent-free process in simple Devices suitable as powder coating crosslinkers can be produced in Combination with commercially available powder coating binders despite a high content deliver coatings of free isocyanate groups and despite high functionality, which are characterized by an excellent flow and very high gloss. this was surprising because according to the teaching of EP-A 639 598 it was to be assumed that such Polyaddition compounds containing ester and / or carbonate groups only up to to a content of free isocyanate groups of a maximum of 2.0 wt .-% for the one Set are suitable as powder coating crosslinkers, especially as also in EP-A 760 380 (P. 7, lines 34 to 40) it should be noted that products with a too high Content of unblocked isocyanate groups due to the unavoidable predecessor wetting in the extruder to form coatings with unsatisfactory optical properties lead companies.

Although in EP-A 669 354 as a suitable starting compound for the solvent free production of polyaddition compounds containing uretdione groups in Intensiv knead hydroxypivalic acid within a long series of simple diols is called neopentylglycol ester, the person skilled in the art of this publication There is no concrete evidence to suggest that uretdione branched out group-containing polyisocyanate mixtures with ester groups and / or carbonate group-containing polyols also in simple stirring apparatus in the melt convert to uretdione powder lacquer crosslinkers with very high total isocyanate contents let that despite a significant proportion of free isocyanate groups and higher Functionality with conventional polyester polyols paint films of excellent Quality. Rather, it can be shown that under exclusive Ver Use of neopentylglycol ester of hydroxypivalate as containing ester groups Branched uretdione group-containing chain extenders Powder coating crosslinkers with free isocyanate groups in contrast to the erfindungsge moderate process products to coatings with significant surfaces disturbances, especially a pronounced orange peel effect.

The present invention relates to polyaddition compounds which are in solid form below 40.degree. C. and in liquid form above 125.degree

• a) with an average isocyanate functionality of 2.1 to 8.0, a content of free isocyanate groups (calculated as NCO; molecular weight = 42) of 2.1 to 6.0% by weight,
• b) a content of uretdione groups (calculated as C ₂ N ₂ O ₂ ; molecular weight = 84) of 10 to 18% by weight,
• c) a content of urethane groups (calculated as -NH-CO-O; molecular weight weight = 59) from 10 to 20% by weight and
• d) a content of ester groups -CO-O (calculated as -CO-O; molecular weight weight = 44) and / or carbonate groups -O-CO-O (calculated as -CO-O; Molecular weight = 44) from 1 to 17% by weight

produced by reacting isocyanate containing uretdione groups components with an average NCO functionality of at least 2.1, excluded pure derivatives of 1-isocyanato- 3,3,5-trimethyl-5-isocyanatomethylcyclohexane, with ester and / or carbonate groups containing polyols, with the exception of neopentyl glycol hydroxypivalate.

The invention also relates to a process for the preparation of polyaddition compounds containing uretdione groups, characterized in that

• A) polyisocyanate mixtures containing uretdione groups and having a medium NCO Functionality of at least 2.1, excluding pure, through trialkyl derivatives of 1-isocyanato-3,3,5-trimethyl-5- produced by phosphine catalysis isocyanatomethylcyclohexane, optionally with the use of
• B) further diisocyanates in an amount of up to 10% by weight, based on the total weight of components A) and B), with
• C) Polyhydroxyl compounds containing ester groups and / or carbonate groups Applications with an average molecular weight of 134 to 2000, except Hydroxypivalinsäureneopentylglykolester, optionally with simultaneous Use of
• D) further polyhydroxyl compounds free of ester groups and carbonate groups Applications of a molecular weight of 62-400 in an amount of up to 70% by weight, based on the total weight of components C) and D), and / or where applicable
• E) further isocyanate-reactive, monofunctional compound applications in an amount of up to 20 wt .-%, based on the total weight of components C), D) and E),

while maintaining an equivalent ratio of isocyanate groups to opposite Isocyanate reactive groups of 1.2: 1 to 1.8: 1 are reacted with one another, with im the other types and proportions of the starting materials mentioned are selected in this way be that the resulting process products the above under a) to d) ge meet the named conditions.

The invention also relates to the use of this polyaddition compound applications as a starting component in the manufacture of polyurethane plastics, especially as a crosslinking component in heat-crosslinkable two-component Polyurethane powder coatings for coating any heat-resistant substrate according to the methods of powder coating technology.

Starting compounds A) for the process according to the invention are through Modification of simple diisocyanates containing uretdione groups isocyanate mixtures which have an average NCO functionality of 2.1 to 2.7.

Suitable diisocyanates for the preparation of these polyisocyanate mixtures are basic additionally those of the molecular weight range 140 to 400 with aliphatic, cyclo aliphatically, araliphatically and / or aromatically bound isocyanate groups, such as z. B. 1,4-diisocyanatobutane, 1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diiso cyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl- 1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclo hexane, 1,3- and 1,4-bis (isocyanatomethyl) cyclohexane, 1,3-diisocyanato-2 (4) - methylcyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyelohexane (Isophorone diisocyanate; IPDI), 1-isocyanato-1-methyl-4 (3) -isocyanatomethylcyclo hexane, 4,4'-diisocyanatodicyclohexylmethane, 1,3- and 1,4-phenylene diisocyanate, 1,3- and 1,4-bis (isocyanatomethyl) benzene, 2,4- and 2,6-tolylene diisocyanate and be dear mixtures of these isomers, diphenylmethane-2,4'- and / or -4,4'-diisocyanate and naphthylene-1,5-diisocyanate and any mixtures of such diisocyanates.

The starting compounds A) used in the process according to the invention Polyisocyanate mixtures containing uretdione groups have a medium NCO Functionality of at least 2.1. It follows that in this polyisocyanate mix in addition to linear bifunctional uretdione structures still further, at least trifunctional polyisocyanate molecules must be present. With these higher functional constituents of the polyisocyanate mixtures A) are esp special about the well-known by-products of diisocyanates with isocyanurate, allo phanate, biuret, urethane and / or iminooxadiazinedione structure.

The preparation of the starting compounds A) can be carried out in different ways Methods are carried out which are generally the customary processes known from the literature for the oligomerization of simple diisocyanates are based, as for example wise in J. Prakt. Chem. 336 (1994) 185-200, DE-A's 16 70 666, 19 54 093, 24 14 413, 24 52 532, 26 41 380, 37 00 209, 39 00 053 and 39 28 503 or the EP A'en 336 205, 339 396 and 798 299 are described.

One way of preparing suitable starting compounds A) is for example wise the direct oligomerization of monomeric diisocyanates to uretdione groups and polyisocyanate mixtures containing higher functional structures in one Step, e.g. B. the dimerization catalyzed by trialkylphosphines and the same early trimerization to give polyiso containing uretdione and isocyanurate groups cyanates (e.g. DE-A 19 34 763 or DE-A 39 00 053).

Suitable starting compounds A) can, however, also be any more obtained step procedures in which uretdione formation and modification to higher functional structures carried out one after the other in any order will. Examples of this type of reaction are, for. That in U.S. 5,461,135 described catalytic dimerization of monomeric diisocyanates and subsequent Implementation of the reaction mixture with alcohols to form uretdione and allophanate group-containing polyisocyanates or those described in WO 99/07765 thermal dimerization with subsequent catalytic trimerization Polyisocyanates containing uretdione and isocyanurate groups.

In addition, particularly suitable starting compounds A) are physical ones Mixtures of separately, for example according to the abovementioned literature known processes, produced with polyisocyanates containing uretdione groups any higher functional polyisocyanates, for example those from Iso cyanurate, allophanate, biuret, urethane and / or iminooxadiazinedione type.

The starting compounds A) used for the process according to the invention Polyisocyanate mixtures containing uretdione groups are generally un indirectly following their production as described above by modification simple diisocyanates by known methods, for example by thin layer distillation or extraction, from the unreacted excess diisocyanate be Friday. They therefore usually have residual levels of monomeric diisocyanates less than 5% by weight, preferably less than 2% by weight, particularly preferred less than 1% by weight.

Regardless of the manufacturing process chosen, the invention Process as starting components A) Polyiso containing uretdione groups cyanate mixtures with a content of uretdione structures of 10 to 25% by weight preferably from 12 to 23% by weight, particularly preferably from 14 to 20% by weight, and an average functionality of 2.1 to 2.7, preferably from 2.1 to 2.5, be especially preferred from 2.1 to 2.3.

Preferred starting compounds A) are uretdione and isocyanurate and / or polyisocyanate mixtures containing biuret groups and based on diiso cyanates with aliphatically and / or cycloaliphatically bonded isocyanate groups type mentioned above by way of example or mixtures thereof. That is particularly preferred Use of polyisocyanates containing uretdione and isocyanurate groups mix based on HDI and / or IPDI.

The use of pure, prepared by trialkylphosphine catalysis Derivatives of IPDI as the sole starting compound A) is in the erfindungsge exempted from normal procedures.

If necessary, further diisocyanates B) can be used in the process according to the invention can also be used. This is, for example, the one described above benen, for the preparation of the starting compounds A) with suitable diisocyanates aliphatically, cycloaliphatically, araliphatically and / or aromatically bound iso cyanate groups. These diisocyanates B) are, if at all, in amounts of up to 10% by weight, preferably up to 5% by weight, based on the total weight of the Components A) and B) are also used. Preferred diisocyanates B) as given may also be used in the process according to the invention Diisocyanates with cycloaliphatically bonded isocyanate groups represent. Especially be The use of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl is preferred cyclohexane and / or 4,4'-diisocyanatodicyclohexyl methane.

In the process according to the invention, there are ester groups and / or carbonate group-containing polyhydroxyl compounds C) with the exception of hydroxy pivalic acid neopentylglycol ester used, which has an average functionality and hydroxyl number calculable molecular weight from 134 to 2000, preferably 176 to 1200, and an average OH functionality of 2.0 to 4.0, preferably of 2.0 to 3.0. These are, for example, the be knew ester alcohols or ester alcohol mixtures, as they are z. B. by Um Settlement of polyhydric alcohols with insufficient amounts of polyhydric alcohols Carboxylic acids, corresponding carboxylic acid anhydrides, corresponding polycarbonate make acid esters of lower alcohols or lactones.

For the preparation of these ester alcohols suitable polyhydric alcohols are in particular those of the molecular weight range 62 to 400 such as. B. 1,2-ethanediol, 1,2- and 1,3-propanediol, the isomeric butanediols, pentanediols, hexanediols, heptanediols and octanediols, 1,2- and 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 4,4 '- (1- Methylethylidene) biscyclohexanol, 1,2,3-propanetriol, 1,1,1-trimethylolethane, 1,2,6- Hexanetriol, 1,1,1-trimethylolpropane, 2,2-bis (hydroxymethyl) -1,3-propanediol or 1,3,5-tris (2-hydroxyethyl) isocyanurate.

The acids or acid derivatives used to make the ester alcohols can be aliphatic, cycloaliphatic, aromatic and / or heteroaromatic Be nature and optionally, e.g. B. by halogen atoms, substituted and / or unge be full. Examples of suitable acids are, for example, polyvalent carbon acids of the molecular weight range 118 to 300 or their derivatives as in for example succinic acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, Trimellitic acid, phthalic anhydride, tetrahydrophthalic acid, maleic acid, maleic acid anhydride, dimeric and trimeric fatty acids, terephthalic acid dimethyl ester and Terephthalic acid bis-glycol ester.

Mixtures of the examples mentioned can also be used to prepare the ester alcohols Starting compounds are used. It is also possible with the erfin according to the method mixtures of different ester alcohols of the type mentioned to use.

Preference is given to starting components in the process according to the invention C) Ester polyols are used, as they are in a manner known per se from lactones and simple polyhydric alcohols as starter molecules with ring opening let ask.

Suitable lactones for the production of these ester polyols are, for example, β-Pro piolactone, γ-butyrolactone, δ-valerolalerone, ε-caprolaprolactone, 3,5,5- and 3,3,5-tri methylcaprolactone or any mixtures of such lactones. As starter molecules serve, for example, the polyhydric alcohols mentioned above by way of example Molecular weight range 62 to 400 or any mixtures of these alcohols.

Particularly preferred polyhydroxyl compounds C) containing ester groups for the process according to the invention are ester diols of the abovementioned molecular weight weight range, especially those based on ε-caprolactone.

Starting compounds C) for the process according to the invention are also provided by Car polyhydroxyl compounds containing carbonate groups. These are to carbonate alcohols of the type known per se, such as, for example, by Um setting of the polyhydric alcohols mentioned above by way of example weight range 62 to 400 with diaryl carbonates, such as. B. diphenyl carbonate, Phosgene or preferably cyclic carbonates, such as. B. trimethylene carbonate or 2,2-dimethyl-trimethylene carbonate (neopentyl glycol carbonate, NPC) or mixtures such cyclic carbonates can be obtained. Particularly preferred carbo Natural alcohols are those obtained from the polyvalent ones mentioned, especially two hydric alcohols as starter molecules and NPCs produced with ring opening can be.

Suitable starting compounds C) for the process according to the invention are in addition, polyhydroxyl compounds containing ester groups and carbonate groups ties. Such ester carbonate alcohols are, for example, according to the teaching of DE-A 17 70 245 by reacting the polyvalent ones mentioned above by way of example Alcohols of the molecular weight range 62 to 400 with lactones of the above type mentioned playfully, in particular ε-caprolactone and subsequent reaction the resulting ester alcohols can be produced with diphenyl carbonate. Preferred however, ester carbonate alcohols are used, as they are due to conversion of the polyhydric alcohols mentioned with mixtures of lactones and cyclic alcohols Allow carbonates to be obtained with ring opening.

The preparation of the above-described, preferably in the case of the invention Process used ester alcohols, carbonate alcohols and ester carbonate alcohols by ring-opening polymerization, generally takes place in the presence of catalyst Sators such as Lewis or Brönsted acids, organic tin or Titanium compounds at temperatures of 20 to 200 ° C, preferably 50 to 160 ° C.

In the process according to the invention, mixtures of the examples can optionally be used Haft mentioned ester alcohols, carbonate alcohols and ester carbonate alcohols as Aus gear component C) are used.

If appropriate, ester groups and can also be used in the process according to the invention Carbonate group-free polyhydroxyl compounds D) of the molecular weight be A rich 62 to 400 can also be used. These are, for example the simple polyvalents described above for the preparation of the ester alcohols gen alcohols or any mixtures of these alcohols. Ester groups and Carbonate group-free alcohols D) are, if at all, in amounts of up to 70% by weight based on the total amount of starting components C) and D) used. Mixtures of Aus suitable for the process according to the invention output components C) and D) also result, for example, when the as Starting material used polyhydric alcohols of the examples mentioned Type with insufficient amounts of acids or acid derivatives, diaryl carbonates or cyclic carbonates of the type mentioned by way of example or phosgene only partially wise in ester groups and / or carbonate groups containing polyhydroxyl compounds applications are transferred.

In the case of the method according to the invention, additional options can optionally be used Isocyanate-reactive, monofunctional compounds E) are also used will. These are, for example, simple aliphatic or cyclo aliphatic monoalcohols such as methanol, ethanol, n-propanol, isopropanol, n- Butanol, isobutanol, sec-butanol, the isomeric pentanols, hexanols, octanols and Nonanols, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol. Cyclohexanol, the isomeric methylcyclohexanols and hydroxymethylcyclohexane. Ether alcohols such as 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, 3-methoxy-1-butanol and glycerol-1,3-di ethyl ether, or ester alcohols such as hydroxyethyl acetate, butyl glycolate, ethyl lactate, Glycerol diacetate or such as can be obtained by implementing the mono mentioned get alcohols with lactones.

These monofunctional compounds E) optionally come in amounts of up to 20% by weight, preferably 15% by weight, based on the total weight of the isocyanate-reactive starting compounds C), D) and E) are used.

Preferred starting compounds E) for the process according to the invention are simple aliphatic or cycloaliphatic monoalcohols of the type mentioned.

To carry out the method according to the invention, the uretdione groups containing polyisocyanate mixtures A), optionally with concomitant use further diisocyanates B) with ester groups and / or carbonate groups Polyhydroxyl compounds C), optionally with the use of other esters group and carbonate group-free polyhydroxyl compounds D) and given if other isocyanate-reactive, monofunctional compounds E) in the mentioned equivalent ratio of isocyanate groups to versus iso cyanate reactive groups from 1.2: 1 to 1.8: 1, preferably 1.25: 1 to 1.6: 1 a reaction temperature of 40 to 200 ° C, particularly preferably from 60 to 180 ° C, preferably vice versa until the theoretically calculated NCO content is reached puts.

In the rest of the nature and proportions of the mentioned Aus gear components selected within the framework of the information provided so that the result tating polyaddition compounds the information given above under a) to d) correspond, with (a) the polyaddition compounds preferably a medium one Functionality from 2.3 to 6.0, particularly preferably from 2.5 to 5.0 and a content of free isocyanate groups of preferably 2.2 to 5.0% by weight, particularly before added 2.4 to 4.0% by weight, and (b) the content of uretdione groups is preferred wise 11 to 17 wt .-%, particularly preferably 12 to 16 wt .-%, (c) the content Urethane groups preferably 12 to 19% by weight, particularly preferably 14 to 18 % By weight and (d) the content of carboxylic acid ester groups and / or carbonate groups is preferably 2 to 12% by weight, particularly preferably 3 to 10% by weight, and the polyaddition compounds being solid below 40.degree. C. and above 125.degree are liquid, especially a differential thermal analysis (DTA) be have a correct melting point or melting range that is within a tempe temperature range from 40 to 110 ° C, particularly preferably within the Temperaturbe range from 50 to 100 ° C.

The polyaddition products according to the invention containing uretdione groups drawing can even at temperatures just a little above their melting point or Melting range is characterized by very low melt viscosities. You let yourself go the process according to the invention very easily in the melt at temperatures produce below the cleavage temperature of uretdione groups. Although with him inventive method, the isocyanate components in a molar excess based on the polyol components are used, fall those according to the invention Process products therefore generally have a low monomer content, i. H. with contents of mono meren diisocyanates of generally less than 1.0% by weight, preferably less than 0.5% by weight, particularly preferably less than 0.3% by weight.

The implementation can also be carried out in special equipment, such as B. intensive kneaders or static mixers, passed through at temperatures in the gap area of uretdione leads to without a major increase in monomeric diisocyanates is observed if there are sufficiently short response times, for example less than 5 minutes.

Of course, the reaction can optionally also in a suitable, ge Solvents which are inert towards isocyanate groups can be carried out. Suitable solutions means for this less preferred procedure are, for example, the per se be knew common paint solvents such as. B. ethyl acetate, butyl acetate, ethylene glycol monomethyl or ethyl ether acetate, 1-methoxypropyl-2-acetate, 2-butanone, 4-methyl 2-pentanone, cyclohexanone, toluene, or mixtures thereof, but also solvents such as Propylene glycol diacetate, diethylene glycol dimethyl ether, diethylene glycol ethyl and -butyl ether acetate, N-methylpyrrolidone and N-methylcaprolactam, or mixtures such solvent.

These solvents, which may also be used, are removed after the reaction has taken place with the help of suitable methods, for example by failure and simple ab suction, spray drying or melt extrusion in an evaporation screw, from the he inventive process product separated.

To accelerate the urethanization reaction can in the invention Process the customary catalysts known from polyurethane chemistry are used be, for example tert. Amines such as triethylamine, pyridine, methylpyridine, benzyl dimethylamine, N, N-endoethylene piperazine, N-methylpiperidine, pentamethyldiethylene triamine, N, N-dimethylaminocyclohexane, N, N'-dimethylpiperazine or metal salts such as Iron (III) chloride, zinc chloride, zinc 2-ethylcaproate, tin (II) octoate, tin (II) ethyl caproate, tin (II) palmitate, dibutyltin (IV) dilaurate and molybdenum glycolate.

These catalysts come optionally in amounts of 0.001 to 2.0 wt .-%, preferably 0.01 to 0.2% by weight, based on the total amount of Aus used connections to use.

The polyaddition compounds according to the invention are valuable starting materials rials for the production of polyurethane plastics after the isocyanate polyaddition process. They are used in particular as a crosslinking component in heat curable, blocking agent-free PUR powder coatings.

Suitable reactants for the polyaddition compounds according to the invention are basically the binders known from powder coating technology isocyanate-reactive groups such. B. hydroxyl, carboxyl, Amino, thiol, urethane or urea groups. Hydroxyfunk is preferred tional powder coating binders are used that are fixed below 40 ° C and above 130 ° C are liquid. The softening temperatures of these hydroxy functional resins - determined by differential thermal analysis (DTA) - are preferably internal half of the temperature range from 30 to 120 ° C, particularly preferably within the Temperature range from 35 to 110 ° C.

Their hydroxyl numbers are between 20 and 200, preferably between 30 and 130 and their mean mole (which can be calculated from the functionality and the hydroxyl content) Cell weight generally between 400 and 10,000, preferably between 1,000 and 5000.

Such powder coating binders are, for example, hydroxyl-containing polyesters, Polyacrylates or polyurethanes, as described in the above-mentioned publications of the Prior art, e.g. B. EP-A 45 998, or EP-A 254 152 are described, but also any mixtures of such resins.

To produce a ready-to-use powder coating, the Polyaddition compounds with suitable hydroxy-functional powder coating binders mixed agents, optionally with other auxiliaries and additives, such as. B. Kata lysers, pigments, fillers or leveling agents added, and for example in Extruders or kneaders above the melting range of the individual components for example 70 to 130 ° C, preferably 70 to 110 ° C, to a homogeneous material united.

The polyaddition compounds according to the invention and the hydroxy-functional ones Binders are used in such proportions that each hydroxyl group 0.6 to 1.4, preferably 0.8 to 1.2 isocyanate groups are omitted, where among isocyanate groups in the polyaddition compounds according to the invention the sum of isocyanate groups present in dimeric form as uretdione groups and free isocyanate groups is understood.

In the case of the Kata, which may also be used to accelerate the hardening process lysers are, for example, the usual ones from polyurethane chemistry known compounds, as already mentioned above in the method according to the invention for Reaction acceleration have been described, or amidines, such as. B. 1,5-diazabi cyclo [4.3.0] non-5-ene (DBN), 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) and 1,2-di methyl-tetrahydropyrimidine, which according to the teaching of EP-A 803 524 is particularly suitable catalysts for lowering the stoving temperatures of uretdione have proven powder coating crosslinkers. These catalysts can optionally in Amounts from 0.01 to 5.0% by weight, preferably 0.05 to 2.0% by weight, based on the Total amount of organic binder, d. H. Polyadditionsver according to the invention bonds in combination with the hydroxy-functional powder coating binders, however excluding any other auxiliaries and additives that may be used will.

The free isocyanates react under the conditions of powder coating production groups of the polyaddition compounds according to the invention, such as by IR spectroscopy Investigations show practically completely. The one after the melt has cooled down resulting, isocyanate group-free solid is then ground and thoroughly Sieving of the grain fractions above the desired grain size, for example above 0.1 mm, exempt.

The ready-to-spray powder coating produced in this way can, according to the usual powder application process drive, such as B. electrostatic powder spraying or vortex sintering, to the coating substrates are applied. According to the invention, any heat-resistant substrates, such as those made of metal, wood or glass, be be layered.

The coatings are hardened by heating to temperatures of 110 to 220 ° C, preferably 130 to 200 ° C, for example for a period of about 10 to 30 minutes. Hard and elastic coatings with good solvent and solvent properties are obtained Chemical resistance, which is characterized by an excellent course and very high Distinguish shine.

Examples

In the following, all percentages, with the exception of the gloss values, relate to the weight.

Output connections A) Polyisocyanate A1)

Uretdione polyisocyanate prepared analogously to Example 3 of EP-A-896 973 based on 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI) with a content of free isocyanate groups of 16.7%, a content of monomeric IPDI of 0.4%, an average NCO functionality of 2.0, a viscosity (according to DIN 53 018) of more than 200,000 mPas (23 ° C) and a content of uretdione groups (determined by hot titration) of 20.9%.

Polyisocyanate A2)

Uretdione and isocyanurate groups prepared analogously to Example 1-a of EP-A-377 177 containing polyisocyanate based on 1,6-diisocyanatohexane (HDI) with a Ge content of free isocyanate groups of 21.8%, a content of monomeric HDI of 0.3%, an average NCO functionality of 2.5, a viscosity (according to DIN 53 018) of 170 mPas (23 ° C) and a content of uretdione groups (determined by Hot titration) of 15.3%.

Polyisocyanate A3)

Uretdione and isocyanurate groups prepared analogously to Example 5 of EP-A 45 995 Containing polyisocyanate based on IPDI with a content of free isocyanate groups of 17.2%, a content of monomeric IPDI of 0.9%, a medium NCO functionality of 2.2, a viscosity (according to DIN 53 018) of more than 200,000 mPas (23 ° C) and a content of uretdione groups (determined by hot titration) of 15.4%.

Polyisocyanate A4)

Isocyanurate polyisocyanate prepared analogously to Example 7 of EP-A 330 966 based on of HDI with a content of free isocyanate groups of 21.8%, a content of monomeric HDI of 0.1%, an average NCO functionality of 3.5 and one Viscosity (according to DIN 53 018) of 3500 mPas (23 ° C).

Polyisocyanate A5)

Biuret polyisocyanate based on, prepared analogously to Example 3 of EP-A 277 353 HDI with a content of free isocyanate groups of 22.0%, a content of monomeric HDI of 0.2%, an average NCO functionality of 4.0 and one Viscosity (according to DIN 53 018) of 11,000 mPas (23 ° C).

Polyisocyanate A6)

Solvent-free isocyanurate polyiso prepared analogously to Example 1 of EP-A 3 765 cyanate based on IPDI with a content of free isocyanate groups of 16.4%, a content of monomeric IPDI of 0.2%, an average NCO functionality of 3.4 and a melting range of 100-105 ° C.

Preparation of the starting compounds C) Diol C1) containing ester groups

620 g of 1,2-ethanediol and 1712 g of ε-caprolactone are mixed at room temperature under dry nitrogen, 0.3 g of tin (II) octoate are added and the mixture is then heated to 160 ° C. for 5 h. After cooling to room temperature, a colorless liquid product is obtained with the following characteristics:
η (23 ° C): 150 mPas
OH number: 476 mg KOH / g
free ε-caprolactone: 0.5%
Average molecular weight (calculated from OH number): 235
Ester group content (calc.): 28.1%

Diol having ester groups C2)

761 g of 1,3-propanediol and 1712 g of ε-caprolactone are mixed at room temperature under dry nitrogen, 0.3 g of tin (II) octoate are added and the mixture is then heated to 160 ° C. for 5 h. After cooling to room temperature, a colorless liquid product is obtained with the following characteristics:
η (23 ° C): 190 mPas
OH number: 449 mg KOH / g
free ε-caprolactone: 0.3%
Average molecular weight (calculated from OH number): 249
Ester group content (calc.): 26.7%

Diol containing ester groups C3)

901 g 1,4-butanediol and 1712 g ε-caprolactone are mixed at room temperature under dry nitrogen, 0.3 g tin (II) octoate is added and the mixture is then heated to 160 ° C. for 5 h. After cooling to room temperature, a colorless liquid product is obtained with the following characteristics:
η (23 ° C): 180 mPas
OH number: 416 mg KOH / g
free ε-caprolactone: 0.1%
Average molecular weight (calculated from OH number): 269
Ester group content (calc.): 25.3%

Triol C4) containing ester groups

1341 g of 1,1,1-trimethylolpropane (TMP) and 1712 g of ε-caprolactone are mixed at room temperature under dry nitrogen, mixed with 0.3 g of tin (II) octoate and then heated to 160 ° C. for 5 h. After cooling to room temperature, a colorless liquid product is obtained with the following characteristics:
η (23 ° C): 2400 mPas
OH number: 546 mg KOH / g
free ε-caprolactone: 0.2%
Average molecular weight (calculated from OH number): 308
Ester group content (calc.): 21.6%

Diol C5 containing carbonate groups)

901 g 1,4-butanediol and 1300 g NPC are mixed at room temperature under dry nitrogen, 0.2 g orthophosphoric acid is added and the mixture is then heated to 160 ° C. for 8 h. After cooling to room temperature, a practically colorless liquid product with the following characteristics is obtained:
η (23 ° C): 1500 mPas
OH number: 519 mg KOH / g
free NPC 0.5%
Average molecular weight (calculated from OH number): 216
Carbonate group content (calc.): 20.0%

example 1

650 g (2.58 eq) of the uretdione group-containing polyisocyanate A1) are mixed at 50 ° C with 350 g (1.82 eq) of the uretdione group-containing polyisocyanate A2) under dry nitrogen, then with 0.1 g of dibutyltin (IV) dilaurate ( DBTL) was added as a catalyst and heated to 80 ° C. To this mixture, which has a uretdione group content of 18.9% and an average NCO functionality of 2.18, a mixture of 207 g (1.76 equiv) of the ester group-containing diol C1) and is added within 20 minutes 55 g (1.77 equiv) of 1,2-ethanediol are added and the mixture is stirred at a maximum reaction temperature of 104 ° C. until the NCO content of the reaction mixture has dropped to a value of 2.9% after about 20 minutes. The melt is poured onto a metal sheet to cool, and a poly addition compound according to the invention is obtained as a pale yellow solid resin with the following characteristics:

NCO content (found / calculated) 2.9 / 2.9% Uretdione group content (calc.) 15.0% Total NCO content (calculated) 17.9% NCO functionality 3.4 monomeric IPDI 0.36% monomeric HDI <0.03% Melting range 79-84 ° C Ester group content (calc.) 4.6% Urethane group content (calc.) 16.5%

Example 2

750 g (2.98 eq) of the uretdione group-containing polyisocyanate A1) are mixed at 50 ° C with 250 g (1.30 eq) of the uretdione group-containing polyisocyanate A2) under dry nitrogen, then with 0.1 g of dibutyltin (IV) dilaurate ( DBTL) was added as a catalyst and heated to 80 ° C. To this mixture, which has a uretdione group content of 19.5% and an average NCO functionality of 2.13, a mixture of 201 g (1.71 eq) of the ester group-containing diol C1) and is added within 20 minutes 53 g (1.71 equiv) of 1,2-ethanediol are added and the mixture is stirred at a maximum reaction temperature of 109 ° C. until the NCO content of the reaction mixture has dropped to a value of 3.0% after about 20 minutes. The melt is poured onto a metal sheet to cool, and a poly addition compound according to the invention is obtained as a pale yellow solid resin with the following characteristics:

NCO content (found / calculated) 3.0 / 2.9% Uretdione group content (calc.) 15.2% Total NCO content (calculated) 17.1% NCO functionality 2.9 monomeric IPDI 0.22% monomeric HDI <0.03% Melting range 76-83 ° C Ester group content (calc.) 4.5% Urethane group content (calc.) 16.1%

Example 3

900 g (3.58 eq) of the uretdione group-containing polyisocyanate A1) are mixed at 50 ° C with 100 g (0.52 eq) of the isocyanurate polyisocyanate A4) under dry nitrogen, then with 0.1 g of dibutyltin (IV) - Dilaurate (DBTL) is used as a catalyst and heated to 80 ° C. To this mixture, which has a uretdione group content of 18.8% and an average NCO functionality of 2.12, a mixture of 221 g (1.64 eq) of the ester group-containing diol C3) is added within 20 minutes. and 74 g (1.64 eq) 1,4-butanediol are added and the mixture is stirred at a maximum reaction temperature of 111 ° C. until the NCO content of the reaction mixture has dropped to a value of 2.8% after about 20 minutes. The melt is poured onto a metal sheet to cool, and a polyaddition compound according to the invention is obtained as a pale yellow solid resin with the following characteristics:

NCO content (found / calculated) 2.8 / 2.7% Uretdione group content (calc.) 14.5% Total NCO content (calculated) 17.2% NCO functionality 2.8 monomeric IPDI 0.31% monomeric HDI <0.03% Melting range 83-88 ° C Ester group content (calc.) 4.3% Urethane group content (calc.) 14.9%

Example 4

900 g (3.58 eq) of the uretdione group-containing polyisocyanate A1) are mixed at 50 ° C. with 100 g (0.52 eq) of the biuret polyisocyanate A5) under dry nitrogen, then with 0.1 g of dibutyltin (IV) dilaurate (DBTL) added as a catalyst and heated to 80 ° C. To this mixture, which has a uretdione group content of 18.8% and an average NCO functionality of 2.14, a mixture of 204 g (1.64 eq) of the ester group-containing diol C2) and is added over the course of 20 minutes 62 g (1.63 equiv) of 1,3-propanediol are added and the mixture is stirred at a maximum reaction temperature of full 106 ° C. until the NCO content of the reaction mixture has dropped to a value of 3.0% after about 20 minutes. The melt is poured onto a metal sheet to cool, and a polyaddition compound according to the invention is obtained as a pale yellow solid resin with the following characteristics:

NCO content (found / calculated) 3.0 / 2.8% Uretdione group content (calc.) 14.8% Total NCO content (calculated) 17.6% NCO functionality 2.9 monomeric IPDI 0.29% monomeric HDI <0.03% Melting range 81-87 ° C Ester group content (calc.) 4.1% Urethane group content (calc.) 15.2%

Example 5

700 g (2.78 eq) of the uretdione group-containing polyisocyanate A1) are mixed at 60 ° C with 300 g (1.17 eq) of powdered isocyanurate polyisocyanate A6) under dry nitrogen, then with 0.1 g of dibutyltin (IV) - dilaurate (DBTL) was added as a catalyst and heated to 80 ° C. To this mixture, which has a uretdione group content of 14.6% and an average NCO functionality of 2.28, a mixture of 197 g (1.58 eq) of the ester group-containing diol C2) and is added over the course of 20 minutes 60 g (1.58 eq) 1,3-propanediol are added and the mixture is stirred at a maximum reaction temperature of 121 ° C. until the NCO content of the reaction mixture has dropped to a value of 3.0% after about 15 minutes. The melt is poured onto a metal sheet to cool, and a polyaddition compound according to the invention is obtained as a light yellow solid resin with the following characteristics:

NCO content (found / calculated) 3.0 / 2.6% Uretdione group content (calc.) 11.6% Total NCO content (calculated) 14.2% NCO functionality 5.3 monomeric IPDI 0.43% Melting range 113-119 ° C Ester group content (calc.) 4.2% Urethane group content (calc.) 14.8%

Example 6

850 g (3.48 eq) of the uretdione and isocyanurate group-containing polyisocyanate A3) are mixed at 50 ° C with 150 g (0.78 eq.) Of the uretdione and isocyanurate group-containing polyisocyanate A2) under dry nitrogen, then with 0, 1 g of dibutyltin (IV) dilaurate (DBTL) was added as a catalyst and heated to 80 ° C. To this mixture, which has a uretdione group content of 15.3% and an average NCO functionality of 2.25, a mixture of 212 g (1.70 equivalents) of the ester group-containing diol C2) and is added over the course of 20 minutes 65 g (1.71 eq) 1,3-propanediol are added and the mixture is stirred at a maximum reaction temperature of 106 ° C. until the NCO content of the reaction mixture has dropped to a value of 2.9% after about 15 minutes. The melt is poured onto a metal sheet to cool, and a polyaddition compound according to the invention is obtained as a light yellow solid resin with the following characteristics:

NCO content (found / calculated) 2.9 / 2.8% Uretdione group content (calc.) 12.0% Total NCO content (calculated) 14.8% NCO functionality 4.5 monomeric IPDI 0.30% monomeric HDI <0.03% Melting range 80-88 ° C Ester group content (calc.) 4.4% Urethane group content (calc.) 15.8%

Example 7

750 g (2.98 eq) of the uretdione group-containing polyisocyanate A1) are mixed at 50 ° C with 250 g (1.30 eq) of the uretdione group-containing polyisocyanate A2) under dry nitrogen, then with 0.1 g of dibutyltin (IV) dilaurate ( DBTL) was added as a catalyst and heated to 80 ° C. To this mixture, which has a uretdione group content of 19.5% and an average NCO functionality of 2.13, a mixture of 185 g (1.71 eq) of the carbonate group-containing diol C5) is added within 20 minutes. and 77 g (1.71 eq) 1,4-butanediol are added and the mixture is stirred at a maximum reaction temperature of 107 ° C. until the NCO content of the reaction mixture has dropped to a value of 2.9% after about 20 minutes. The melt is poured onto a metal sheet to cool, and a polyaddition compound according to the invention is obtained as a pale yellow solid resin with the following characteristics:

NCO content (found / calculated) 2.9 / 2.8% Uretdione group content (calc.) 15.5% Total NCO content (calculated) 17.7% NCO functionality 2.9 monomeric IPDI 0.293% Melting range 80-86 ° C Carbonate group content (calc.) 2.9% Urethane group content (calc.) 16.0%

Example 8

900 g (3.58 eq) of the uretdione group-containing polyisocyanate A1) are mixed at 50 ° C with 100 g (0.52 eq) of the isocyanurate polyisocyanate A4) under dry nitrogen, then with 0.1 g of dibutyltin (IV) - Dilaurate (DBTL) is used as a catalyst and heated to 80 ° C. To this mixture, which has a uretdione group content of 18.8% and an average NCO functionality of 2.12, a mixture of 126 g (0.82 eq) of the ester group-containing triol C4) is added within 20 minutes. , 167 g (1.24 eq) of the ester group-containing diol C3) and 56 g (1.24 eq) 1,4-butanediol and stirred at a maximum reaction temperature of 113 ° C until the NCO content of the reaction mixture after approx. 15 min has dropped to a value of 2.8%. The melt is poured onto a metal sheet to cool, and a polyaddition compound according to the invention is obtained as a light yellow solid resin with the following characteristics:

NCO content (found / calculated) 2.8 / 2.5% Uretdione group content (calc.) 14.0% Total NCO content (calculated) 16.5% NCO functionality 5.3 monomeric IPDI 0.41% monomeric HDI <0.03% Melting range 87-94 ° C Ester group content (calc.) 5.1% Urethane group content (calc.) 14.4%

Example 9 (comparison)

650 g (2.58 eq) of the uretdione group-containing polyisocyanate A1) are mixed at 50 ° C 350 g (1.82 eq) of the uretdione group-containing polyisocyanate A2) under dry conditions Nitrogen mixed, then with 0.1 g of dibutyltin (IV) dilaurate (DBTL) as Added catalyst and heated to 80.degree. To this mixture that has a content of Has uretdione groups of 18.9% and an average NCO functionality of 2.18, 158 g (3.51 eq) 1,4-butanediol are added within 30 minutes. Already during the Diol addition has to be due to the rapidly increasing viscosity of the reaction mixture To further ensure stirrability, the heating bath temperature is increased to 135 ° C will. After 10 minutes the NCO content of the reaction mixture is 4.1%. To The temperature of the reaction mixture has risen further due to the 20 min Viscosity under the action of the shear forces occurring during stirring in spite of a constant outside temperature from 135 ° C to 158 ° C. The NCO Ge halt has increased to 5.2% and does not decrease even with longer reaction times off again. The monomeric IPDI content is 1.9%.

Example 10 (comparison)

650 g (2.58 eq) of the uretdione group-containing polyisocyanate A1) are mixed at 50 ° C 350 g (1.82 eq) of the uretdione group-containing polyisocyanate A2) under dry conditions Nitrogen mixed, then with 0.1 g of dibutyltin (IV) dilaurate (DBTL) as Added catalyst and heated to 80.degree. To this mixture that has a content of Has uretdione groups of 18.9% and an average NCO functionality of 2.18, 358 g (3.51 eq) of hydroxypivalin are added in portions over the course of 30 minutes acid neopentyl glycol ester to. Already towards the end of the addition of diol must be because of the strong increasing viscosity of the reaction mixture raises the heating bath temperature to 130 ° C must be increased in order to continue to ensure the ability to stir. After 15 minutes the NCO content of the reaction mixture 3.5%. After 20 minutes, the temperature of the Reaction mixture due to the further increased viscosity under the one effect of the shear forces occurring during stirring despite a constant exterior temperature increased from 130 ° C to 151 ° C. The NCO content has increased to 4.2% does not increase and decrease again even with a longer reaction time. The content of monomeric IPDI is 1.4%.

Comparative Examples 9 and 10 show that in the implementation of branched. Polyisocyanate mixtures containing uretdione groups with simple diols or Hy neopentylglycol droxypivalate in the melt corresponding to that in Example 1 Uretdione cleavage occurs to a considerable extent. The indicated aimed at NCO contents of 3.2% (Example 9) and 2.8% (Example 10) are not achieved, the levels of monomeric diisocyanate exceed the limit of 1% significantly lich.

Example 11 (comparison)

650 g (2.58 eq) of the uretdione group-containing polyisocyanate A1) and 350 g (1.82 eq) of the uretdione group-containing polyisocyanate A2) are added to 1358 g of anhydrous toluene with 0.1 g of dibutyltin (IV) dilaurate (DBTL) as a catalyst 80 ° C submitted under dry nitrogen. 358 g (3.51 eq) of neopentylglycol hydroxypivalate are added in portions to this solution, which has a uretdione group content of 8.0%, over a period of 30 minutes and the mixture is stirred at a reaction temperature of 100 ° C. until the NCO content is reached has decreased by 1.4%. The yellowish solution obtained is then completely freed from solvent by spray drying in a commercially available Minispray Dryer 190 laboratory spray dryer (from Büchi). A light yellow product is obtained with the following characteristics:

NCO content (found / calculated) 2.7 / 2.7% Uretdione group content (calc.) 13.9% Total NCO content 16.6% NCO functionality 3.4 monomeric IPDI 0.15% monomeric HDI <0.03% Melting point 97-101 ° C Ester group content (calc.) 5.7% Urethane group content (calc.) 15.2%

Example 12 (usage)

55.1 parts by weight of a commercially available polyester containing hydroxyl groups (Crylcoat® 240, from UCB Chemicals) with an OH number of 30 are mixed with 6.9 parts by weight of polyaddition compound according to the invention from Example 1, corresponding to an equi valent ratio of total NCO to OH of 1: 1, 1.5 parts by weight of a commercially available leveling agent (Modaflow® Powder III, Solutia), 1.0 part by weight of tin (II) - palmitate as a catalyst, 0.5 part by weight of benzoin and 35.0 parts by weight of a white pigmentes (Kronos 2160, from Kronos Titan) mixed thoroughly and then mixed with With the help of a Buss Cokneter type PLK 46 at 100 rpm and a housing homogenized temperature of 100 to 120 ° C in the process section. After cooling it will the solidified melt using an ACM 2 classifier mill (Hosokawa Mikropul) ground with a 90 µm sieve and sieved. The powder obtained in this way, which according to IR spectroscopic investigations no longer contains free isocyanate groups with an ESB cup gun at a high voltage of 70 kV on a degreased one Sheet steel sprayed and cured at 180 ° C for 15 minutes.

For comparison, an analogue of 54.6 parts by weight of the same is used for hydroxyl groups term polyester with 7.4 parts by weight of the poly obtained according to Comparative Example 11 addition compound, 1.5 parts by weight of a commercial leveling agent (Modaflow® Powder III, Solutia), 1.0 part by weight of tin (II) palmitate as kata lysator, 0.5 part by weight of benzoin and 35.0 parts by weight of a white pigment (Kronos 2160, from Kronos Titan) produced a powder coating, ge on a degreased sheet steel injected and also cured for 15 min at 1805 ° C. The equivalent ratio of Ge including NCO to OH is also 1: 1.

Both coatings were then examined in terms of paint technology. In addition to gloss and haze values, the orange peel effect measured with the aid of a "wave-scan plus" device from Byk-Gardner was used to characterize the surface structure. The following properties are found at layer thicknesses of approx. 60 µm:

The comparison shows that with the aid of the polyaddition compound according to the invention a fully crosslinked paint film is obtained, which is opposite to the coating that using the known polyaddition compound of the prior art was produced by a considerably higher elasticity, a higher gloss, ge lower turbidity and a significantly better course. During the inven The comparative coating shows that the paint film obtained in accordance with the invention ran smoothly a strong orange peel structure.

Example 13 to 15 (usage)

According to the method described in Example 12, starting from the hydroxyl-containing polyester described in Example 12 and the polyaddition compounds 2, 3 and 6 according to the invention, white pigmented powder coatings are Herge. The fully formulated powder coatings, which according to IR spectroscopic investigations are free of unblocked isocyanate groups in all cases, are each sprayed onto degreased sheet steel with an ESB cup gun at a high voltage of 70 KV and cured for 15 minutes at 180 ° C. The table below shows the compositions (parts by weight) of the powder coatings and the technical characteristics of the coatings obtained therefrom (layer thickness in each case about 60 μm).

Claims (7)

1. Polyaddition compounds which are in solid form below 40 ° C and in liquid form above 125 ° C and

• a) with an average isocyanate functionality of 2.0 to 8.0, a content of free isocyanate groups (calculated as NCO; molecular weight = 42) of 2.1 to 6.0% by weight,
• b) a content of uretdione groups (calculated as C ₂ N ₂ O ₂ ; molecular weight = 84) of 10 to 18% by weight,
• c) a content of urethane groups (calculated as —NH — CO — O; molecular weight = 59) of 10 to 20% by weight and
• d) a content of ester groups -CO-O (calculated as -CO-O; molecular weight = 44) and / or carbonate groups -O-CO-O (calculated as -CO-O; molecular weight = 44) of 1 to 17 wt .-% exhibit

produced by reacting uretdione-containing isocyanate components with an average NCO functionality of at least 2.1, with the exception of pure derivatives of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, with ester and derivatives, prepared by trialkylphosphine catalysis / or polyols containing carbonate groups, with the exception of neopentyl glycol esters. 2. A process for the preparation of polyaddition compounds containing uretdione groups, characterized in that one

• A) Polyisocyanate mixtures containing uretdione groups and an average NCO functionality of at least 2.1, with the exception of pure derivatives of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane produced by trialkylphosphine catalysis, optionally with the use of
• B) further diisocyanates in an amount of up to 10% by weight, based on the total weight of components A) and B)
• C) Polyhydroxyl compounds containing ester groups and / or carbonate groups and an average molecular weight of 134 to 2000, with the exception of neopentylglycol ester hydroxypivalates, if necessary with the simultaneous use of
• D) further ester groups and carbonate groups-free polyhydroxyl compounds with a molecular weight of 62-400 in an amount of up to 70% by weight, based on the total weight of components C) and D), and / or optionally
• E) further isocyanate-reactive, monofunctional compounds in an amount of up to 20% by weight, based on the total weight of components C), D) and E),

while maintaining an equivalent ratio of isocyanate groups to isocyanate-reactive groups of 1.2: 1 to 1.8: 1, with the rest of the nature and proportions of the starting materials mentioned being chosen so that the resulting process products correspond to the above under a) to d) meet the specified conditions. 3. The method according to claim 2, characterized in that one is used as the starting point compounds A) polyisocyanate mixtures containing uretdione groups Based on diisocyanates with aliphatically and / or cycloaliphatically bound Isocyanate groups, except pure ones, are produced by trialkylphosphine catalysis derivatives of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclo hexane. 4. The method according to claim 2, characterized in that one is used as the starting point compounds A) Polyisocyanate containing uretdione and isocyanurate groups mixtures based on 1,6-diisocyanatohexane and / or 1-isocyanato-3,3,5-tri methyl-5-isocyanatomethylcyclohexane, except pure, by trialkyl derivatives of 1-isocyanato-3,3,5-trimethyl-5- produced by phosphine catalysis isocyanatomethylcyclohexane, is used. 5. The method according to claim 2, characterized in that as Polyhy hydroxyl compounds C) by ring-opening polymerization of ε-caprolactone manufactured polyester polyols are used. 6. Use of the polyaddition compounds according to Claim 1 as a starting point component in the manufacture of polyurethane plastics. 7. Use of the polyaddition compounds according to Claim 1 as crosslinking agents component in heat-crosslinkable two-component polyurethane powder paint when coating any heat-resistant substrates according to the Methods of powder coating technology.